There are currently available several strains of rats which have been selectively bred for hypertension. These serve as genetic animal models for human essential hypertension. All such models are multigenic, i.e. more than one gene is involved in causing the genetic hypertension. My purpose is to look for biochemical differences between the genetically hypertensive strains and their corresponding normotensive control strains. When a biochemical parameter is identified which differs between strains, genetic studies are done a) to define the mode of inheritance of the parameter and b) to find out if the parameter and an increment of blood pressure segregate together in an F2 population. Specific areas of investigation include adrenal steroids and newly described pituitary proteins. The two strains of rats developed by the late Lewis Dahl are under study. One strain is highly susceptible (S) and the highly resistant (R) to the hypertensive effect of high salt diet. I have found that R pituitaries carry four electrophoretically defined proteins absent in S rats. Work with these proteins will be directed at 1) isolation and physical characterization, 2) development of a radioimmunoassay, 3) determination of immunologic relationships among the four proteins and with other proteins, 4) investigation of biological activities for these proteins, especially as this may involve sodium metabolism.